Consistency of crown rust evaluation in ryegrass cultivars

Crown rust (Puccinia coronata) is the most important leaf disease in forage ryegrasses (Lolium spp.). In order to evaluate the stability in space and time of crown rust resistance a multisite rust evaluation trial was established by the European breeders association Eucarpia ( Fodder Crops Section). The same seed lots of 33 perennial ryegrass (Lolium perenne) and 18 Italian ryegrass (Lolium multiflorum) varieties were sown in April 2001, 2004 and 2007 at 27 European sites. This paper reports the temporal ranking of the ryegrass varieties for their crown rust susceptibility at the Belgian site and compares this ranking with the mean ranking over the European sites. The crown rust susceptibility was scored in September of each sowing year and of the year after. The rankings of both the perennial and the Italian ryegrass varieties were well correlated between the successive yearly observations at each sowing period. Also the rankings of the varieties of both species were similar over the 3 sowing periods. The rankings at the Belgian site corresponded very well with the mean ranking over the European sites. The crown rust resistance in ryegrass seems to be durable and consistent over a great part of Europe.